An X-ray examination apparatus of this kind comprises a sensor matrix with a plurality of sensors, for example 2000.times.2000 sensors which are arranged in rows and columns. Each of these sensors comprises an X-ray sensitive photosensor element. In each sensor a storage capacitance is connected parallel to the photosensor element. For example, the stray capacitance of the photosensor element can be used for the storage capacitance. The first electrodes of the photosensor element and the storage capacitance are connected to a counter-electrode which receives a positive or a negative direct voltage, depending on the connection of the photosensor element. The other two electrodes of the photosensor element and the storage capacitance can be connected to a read line via an electric switch. Prior to the execution of an X-ray exposure during which an object to be examined is exposed to the X-rays, the electric switches of all sensors are briefly closed, i.e. switched to the conductive state. After completion of the exposure, the switches of the sensors are closed again to enable reading of the charges stored in the storage capacitances after the X-ray exposure. However, this read operation is not performed simultaneously for all sensors. Only as many sensors can be read simultaneously as there are read lines provided in the sensor matrix. Sensors connected to a common read line are read sequentially in time.
Devices for measuring the intensity of the X-ray exposure are not known for such X-ray examination apparatus. For X-ray examination apparatus utilizing an X-ray image intensifier and optically coupled cameras it is known to uncouple the intensified light optically from the exit screen of the X-ray image intensifier for supply to a light detector for measuring the intensity of the exposure. Such a device is known, for example from EP-A-0 200 272 which corresponds to U.S. Pat. No. 4,747,118 but cannot be utilized for an X-ray examination apparatus of the kind set forth.